# Edexcel GCSE Science Core Practicals: Checked Through and Improved

Joshua Davis.

Edexcel GCSE Science Core Practicals: improved version.

Note: although this is an improved version, I still cannot guarantee that it is free from mistakes. If in doubt, always check with Bitesize, your teacher, etc.

## Key:

Italics: necessary equipment.

Independent variables are things you change. Dependant variables are the thigst yourey you’re measuring.

Control variables are the things you keep the same.

## Biology.

### Looking at cells (AKA making you know how to use a microscope).

1. Get a microscope.

2. Twist the lowest-power lens (x10) into line with the stage (the bit of the microscope you put the stuff you’re looking at onto).

3. Put the microscope slide (the bit of glass with the specimen (thing you look at) in it) onto the stage. Make sure the specimen is on top of the hole in the stage (because this is where the light passes through).

4. Look into the microscope (through the eyepiece).

5. Turn the coarse focus (the bigger dial (normally) under the stage. It moves the stage up and down) backwards and forwards until the image is clear.

6. Draw what you see.

7. Twist the medium-power lens (x40) into line with the stage.

8. Turn the fine focus (the smaller dial (normally) under the stage. It moves the stage up and down) backwards and forwards until the image is clear.

9. Draw what you see.

10. Repeat Steps 7-9 with the high-power lens (x100).

### Food tests (AKA using chemicals to find out whether stuff is in a food sample (bit of food)).

#### #1: Finding out whether starch is in the food.

1. Get one spatula (for solids) or 1cm3 (for liquids) of the food (or drink).

2. Put it onto the food dish.

3. Drop a few drops of iodine solution onto the food (with a dropper).

4. If it turns bluey-black (navy), there’s strach. If it stays orangey-brown, there isn’t.

#### #2: Finding out whether reducing sugars (generally glucose) is in the food.

1. Get two spatulas (for solids) or 1cm3 (for liquids) of the food (or drink).

2. Put it/them into a test tube.

4. Mix.

5. Add an equal amount of Benedict’s solution.

6. Put the test tube into a water bath (set to about 95°C) for a few minutes.

7. If the mixture has a low concentration of reducing sugars, it’ll be green or yellow. If it has a high concentration, it’ll be brick-red. If there’re no reducing sugars, it’ll stay blue.

#### #3: Finding out whether protein is in the food.

1. Get a piece of the food.

2. Break the food up in a pestle and mortar.

3. Transfer this to a beaker.

4. Add some distilled water.

5. Stir (with a glass rod). This dissolves some of the food.

6. Line a funnel with some filter paper and put another beaker underneath it.

7. Filter the solution to remove the solid bits of food (that weren’t able to dissolve). The filtrate (liquid that passed through the filter) is a food sample. :)

8. Put 2cm3 of