Year 9 Science

Christmas Exam

Thermal Energy

Thermal Energy is heat energy. Heat is transferred from Hot areas to Cold areas. The picture shows heat moving away from the hot tea to the cooler surroundings. This heat can be transferred by:

· Conduction

· Convection

· Radiation

Temperature is the measurement of heat energy.

This is done using a Thermometer, with the units Degrees Celsius, °C.

Conduction of Heat

Conduction is the main method of thermal energy transfer in solids.

When a substance is heated, the atoms start to move around (vibrate) more.
As they do so they bump into each other, transferring energy from atom to atom.
The heat is conducted along the material from hot to cold.

Metals are extremely good at conducting heat. Non-metals are bad at conducting heat whilst liquids and gases are extremely bad. Bad conductors are called insulators. Plastic is a poor conductor of heat and is used sometimes as a handle for saucepans.

Investigating Conduction

Investigating Conduction – Conduction Rods

All metals are good conductors of heat, but some are better than others.

In this experiment the metals are all heated at one end.

The heat conducts along the metals and melts the Vaseline/wax holding the pins.

The rod with the pin that falls off first is the best conductor of heat. Copper is one of the best conductors of heat.

Convection of Heat

Convection is the main way that heat travels through liquids and gases (Convection cannot happen in solids as the particles in solids cannot flow and move).

· The particles are heated and expand then rise up because they are lighter.

· As they move away from the heat, they cool, become heavier and fall.

Radiation of Heat

All objects give off thermal radiation. The hotter an object is, the more thermal radiation it emits. Thermal radiation is the part of the electromagnetic spectrum called infrared.

Thermal radiation is the only way in which heat can travel through a vacuum. It is the way in which heat reaches us from the Sun through the vacuum of space.

The colour of an object affects how good it is at emitting and absorbing thermal radiation:

Dark (Matt Black) objects are good at emitting heat radiation and absorbing heat radiation.

A black surface will absorb heat easily and get hot very quickly.

A silvery shiny surface will reflect heat and absorb heat slowly.

Thermos Flask

A thermos flask reduces heat loss by conduction, convection and radiation.

· The inside is shiny reducing the loss of heat by radiation.

· It has a plastic lid to reduce heat loss by convection.

· The vacuum layer between the inside and outside of the flask reduces heat loss by conduction.

A thermos not only keeps hot things hot by reduction the movement of heat out of the flask. It also keeps cold things cold by preventing heat getting.

Investigating Insulation

Some materials are better insulators than others. Heat is easily lost of there is no insulation.

The temperature of objects with different insulating materials can be measured and the object can be allowed to cool over time.

The object that loses the least heat over that time is the best insulator.

Insulating your Home

Lots of money is spend heating our homes.

But heat is lost through the windows, doors, roof and walls. By insulating out homes we can reduce heat loss:

· Cavity wall insulation

· Fibreglass loft (roof) insulation

· Double Glazing windows

· Thick carpets on floors

Revision Notes - Variation

Differences in individuals of the same species or between different species is known as Variation. There may be variation in height, weight, eye colour etc.

We inherit some of our features from our parents eg. hair colour, eye colour, height etc.

Other features are caused by our environment eg. scars, hair length etc.

Most cells in our body have a Nucleus which contain thread-like structures called

Chromosomes. Every human body cell contains 46 chromosomes (23 pairs).

However, sex cells such as sperm and egg cells contain only 23 chromosomes.

DNA, Genes, Chromosomes, Nucleus and the Cell

Genes are found on Chromosomes and these contain instructions for inheritance such as eye-colour, hair colour, height etc. Each Gene contains strands of smaller DNA in a spiral Double Helix shape. Chromosomes are packed into the Nucleus of the Cell.

Fertilisation and Pregnancy

When the sperm cell fertilises the egg cell in the Oviduct, a Zygote cell is formed. This zygote cell grows and divides into two cells.

These two cells grow and divide into 4 cells and so on. Millions of specialised cells form and develop into an embryo and a foetus – 9 months later a baby is ready to be born.

This bundle of cells implants into the wall of the uterus, as they baby develops.

As the foetus develops and gets larger, the cells in it needs a supply of nutrients and oxygen.

A placenta forms. This provides a link between the mothers blood and the baby’s blood to exchange these nutrients.

Anything the mother eats or drinks, including drugs and alcohol can transfer into the baby and harm the developing baby.

Waste products and Carbon Dioxide from the baby transfer into the mother’s blood.

The amniotic fluid in the amniotic sac surrounds the baby and protects the baby as it develops.

Female Reproductive Organs

Male Reproductive Organs

Measuring the Types of Variation

Variation can be caused by the Genes inherited from parents or from the Environment. A person may inherit the ability to roll their tongue from their parents but their height might be affected by the nutrition in their diet, their environment.

Male and Female Changes During Puberty

Acid and Alkali

Acids and alkalis are corrosive. Acids and alkalis are chemical opposites.

Indicators can be used to show which substances are Acids and which things are Alkalis, or even Neutral. Universal Indicator is an indicator that shows how strong or weak an acid or alkalis is, or if the chemical is Neutral. The colour change is matched to the pH Scale. There are 14 different numbers and colours on the pH Scale. A Digital pH meter is a very accurate way of measuring the pH of a substance.

· Acids have a pH between 0-6 (Hydrochloric Acid pH1)

· Neutrals are exactly 7 (Water pH 7)

· Alkalis have a pH between 8-14 (Sodium Hydroxide pH14)

Making an Indicator

Lots of fruit and veg have natural juices that can be used to make an indicator eg. Red Cabbage. The steps include:

1. Chop up cabbage

2. Boil cabbage in water

3. Filter the cabbage leaves

4. Use the water as indicator

Neutralisation

If two equal volumes and concentrations of Acid and Alkali are reacted it will produce a Neutral Solution made from Salt and Water.

The name and type of the salt formed depends on the acid and alkali that are neutralised:

Useful Neutralisation

Neutralisation reactions can be useful. A lot of food and drinks (vinegar) are slightly acidic, pH4, and damage our teeth causing decay. Toothpaste is slightly alkaline and neutralises the acid – reducing tooth decay.

Revision Notes - Printable Version

Year 9 Science Assessment 1 - Xmas Revision Notes New.pdf

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